Structure and phase composition of binary Al–Zn, Al–Mg and ternary Al–Zn–Mg alloys were studied before and after high pressure torsion (HPT) with shear strain 300. The size of (Al) grains and crystals of reinforcing second phases decreases drastically after HPT reaching nanometer range. As a result of HPT, the Zn-rich (Al) supersaturated solid solution decomposes completely and reaches the equilibrium state corresponding to room temperature. The decomposition is less pronounced for Al–Mg and Al–Zn–Mg alloys. We conclude that the severe plastic deformation of supersaturated solid solutions can be considered as a balance between deformation-induced disordering and deformation-accelerated diffusion towards the equilibrium state.